<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<script>
var a={};
var b={
    key:'a',
};
var c={
    key:'c',
};
a[b]='123'; //a["{key:'a'}"]
a[c]='456'; //a["{key:'c'}"]
console.log(a[b],a[c]);  //456


</script>
</body>
</html>